1. Field of the Invention
This invention relates in general to large diameter, threaded conductor pipe used for offshore drilling, and in particular to an apparatus for breaking out a lower joint of the conductor pipe when the well is suspended.
2. Description of the Prior Art
When drilling from a jackup drilling rig in offshore drilling, large diameter conductor pipe will extend from a selected depth in the earth to a point above the surface of the water and below the rig floor. The conductor pipe will be installed by screwing the threads of the conductor pipe sections together. The uppermost section of conductor pipe will be cut off at a desired point below the rig floor. The threaded connection at the sea floor or slightly above will be a left-hand thread. The rest of the threads will be right-hand.
After drilling the well, often the well will be suspended. The drilling rig will be moved away from the well. It will be necessary to remove the portion of the conductor pipe that extends above the sea floor to the drilling rig. The portion of the conductor pipe that extends into the earth will remain in place.
In the past, this has been a difficult task. Generally, the operator will try to grip the upper section of conductor pipe with a spear or the like, then rotate it to the right. Hopefully, this will cause the lower connection to break out. Then the operator will pull the entire string upward, disconnecting each section one at a time.
Because of the weight of the conductor string on the left-hand threaded joint, there will be a lot of friction at the box nose/pin shoulder interface. This makes it difficult to apply enough torque from the surface to break out this joint. Also, it is difficult to lift the conductor string because there will be no external thread collar at the upper end of the conductor string.